Method of using SNR to reduce factory test time

ABSTRACT

The application relates to wireless networks and more particularly to a method of reducing factory test time of receiver sensitivity in a Code Division Multiple Access (CDMA) wireless device. Under TIA/EIA/-98E, the radio frequency (RF) sensitivity of a CDMA wireless receiver is the minimum received power, measured at the mobile station antenna connector, at which the frame error rate (FER) does not exceed 0.5% with 95% confidence. In order to reduce the test time of FER test method, the relation between correlated energy (or Ec/Io) and FER is determined using simulated traffic and the correlated energy (or Ec/Io) measurement is then used as the test parameter on like models to achieve the same or superior test confidence with significantly reduced test time.

COPYRIGHT NOTICE

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BACKGROUND OF THE INVENTION

1. Field of Invention

The application relates to wireless networks and more particularly to amethod of reducing factory test time of receiver sensitivity of awireless device, such as a Code Division Multiple Access (CDMA) wirelessdevice.

2. Description of the Related Prior Art

As shown in FIG. 1, the delivery end of a typical mobile communicationsystem 100 is divided into a number of cells 110 or geographicalcoverage areas, within each of which is a base station 120. Alternately,base station 120 for a number of cells 110 is co-located at theintersection of those cells and directional antennas are used to providecoverage over the area of each adjacent cell. Each base station 120contains radio transmission and reception equipment for communicatingwith a wireless device 130, such as mobile phone, laptop, personaldigital assistant (PDA) or the like, located within the associated cell110. The coverage area of a given cell 110 is dependent upon a number offactors such as transmit/receive capabilities of the base station 120and/or wireless device 130, the antenna (not shown) of base station 120,and the topology of the area. Specific radio frequencies are allocatedwith each cell 110. In a CDMA wireless network, the same frequency isreused in every cell. Each base station 120 connects to a backboneinfrastructure (not shown) which perform a variety of functions such asthe set up and tear down of call and the handoff of calls from one basestation 120 to another.

FIG. 2 depicts a representative CDMA receiver block 200 for wirelessdevice 130. Antenna 210 receives radio frequency signal 220 from basestation 120 and converts it into a current on a conductor. The signal isvery weak from absorption so, after passing through duplexer 230 (whichsimply permits a single antenna system to be used for both transmittingand receiving) the signal is amplified in low noise amplifier (LNA) 240.The signal is then passed through filter 250 to eliminate out-of-bandnoise and interference. In order to recover the original informationsignal from the modulated radio frequency signal 220, the signal is sentthrough mixer 260 which is fed by local oscillator (LO) 270 at the samefrequency as the one in the transmitter (not shown) of base station 120if, as shown in FIG. 2, zero intermediate frequency (IF) technology isused. Alternatively, there may be more than one mixer 260 to mix thereceived signal 220 down to at least one non-zero intermediate frequencyand then down to a baseband signal by multiple steps. Out of the mixer260 come two frequency signals (sum and difference). One of thefrequencies is the intermediate frequency, the other is eliminated byfilter 280. The resulting signal is amplified by amplifier 290, andpassed through analog to digital converter 300 for digital processing inbaseband processor 310 which may include a RAKE receiver. As thoseskilled in the art will appreciate, wireless device 130 is a transceiverin that it incorporates both transmitter (Tx) and receiver (Rx)functionality (e.g. the power amplifier (PA) associated with thetransmitter is shown in FIG. 2). As will also be appreciated, the signalprocessing system of wireless device 130 may be comprised of multipleanalog and mixed signal integrated circuit (IC) chips (such asamplifiers, filters, A/D and D/A converters), digital IC chips (such asmemory, digital signal processors (DSP), and microprocessors) and manypassive discrete components.

Quality assurance measures at the factory level ensure that wirelessdevice 130 operates satisfactorily. Various standards have beendeveloped against which wireless device 130 is measured. One suchstandard is a Telecommunications Industry Association/ElectronicIndustries Association standard, TIA/EIA/-98E, which defines recommendedminimum performance standards for cdma2000 spread spectrum mobilestations. More specifically, a test is established in this standard forreceiver sensitivity and dynamic range. The radio frequency (RF)sensitivity if a cdma2000 mobile station receiver is the minimumreceived power, measured at the mobile station antenna connector, atwhich the frame error rate (FER) does not exceed 0.5% with 95%confidence. In CDMA systems, the frame is the basic physical channeldata packet, typically having a 20 ms transmission time that consists ofinformation on the traffic channel (voice or data). Because the linkbetween base station and handset is established on a frame-by-framebasis the performance of a CDMA mobile phone is evaluated in terms ofits FER. Regarding receiver sensitivity, two sources of interference arepurely additive white Gaussian noise (AWGN): the receiver'sinput-referred thermal noise power spectral density (N_(o)) and thetransmitter's thermal noise power spectral density (N_(Tx)) in thereceiver frequency band (see FIG. 2). A typical sensitivity and dynamicrange test setup using FER is shown in FIG. 3A while the associated testparameters as defined in TIA/EIA/-98E are shown in FIG. 3B. Asensitivity test (test 1) ensures the receiver's ability to receive weaksignals, and a dynamic range test (test 2) ensures the receiver'sability to receive a strong signal. In FIG. 3A, the base station 120 issimulated using a piece of test equipment 320, such as the Agilent 8960wireless communications test set, which feeds a test signal to anantenna port of a device under test (DUT) 330. As highlighted in FIG.3B, a typical test, at 9600 bps (RC 1 and 3) or 14400 bps (RC 2) datarate, consists of setting the test parameters of Test 1 or Test 2, andcounting the number of frames transmitted at the base station andcomparing it to the number of erroneous frames received at the mobilestation.

One of the problems with the TIA/EIA/98E receiver sensitivity test isthat the test time is too long for mass production, being physicallyrestricted by the arrival rate of the frames at DUT 330. In an attemptto reduce the test time, the maximum number of frames for thesensitivity test is limited to no more than 1000 (which may not alwaysachieve the required 95% confidence level), but this method still takesup to 80 seconds for four channels at two bands. As will be appreciated,for thousands of units, the test time and associated cost in man hoursmay become prohibitive.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the FER test method, there isprovided an improved receiver sensitivity test. For a given model ofCDMA wireless device the relation between correlated energy or SNR andFER is determined using simulated traffic and the correlated energy orSNR measurements are then used as the test parameters on like models toachieve the same or superior lest confidence with significantly reducedtest time. Because the test is conducted over a time-invariant AWGN, andgiven the fact that the digital signal processing is identical to allDUT 330 of the same type, the frame error rate is only dependent on thecorrelated energy or SNR at the output of A/D 300 feeding to thebaseband processor 310. Baseband processor 310 of a CDMA wireless device130 includes an Ec/Io estimator (energy per chip to interference densityratio, which is a kind of expression of SNR often used in a CDMA basedsystem), which is borrowed for the factory test. The Ec/Io estimate isdetermined by a RAKE linger energy estimator (producing an outputrelated to correlated “energy”) found in baseband processor 310, andsome further processing which translates the estimated correlated energyto Ec/Io. Both Ec/Io and the correlated energy are monotonic functionsof frame error rate under a given channel condition, so either can beused. Since the estimator reported correlated energy (or Ec/Io) containsa certain degree of random fluctuations, its distribution and nonlinearrelation with frame error rate is characterized for a given model ofwireless device, to determine a set of factory test criteria thatachieves a test confidence level equal or superior to the TIA/EIA/-98Ereceiver sensitivity test. Once the characterization is carried out,each wireless device 130 is evaluated against the established pass/failcorrelated energy or Ec/Io threshold.

In accordance with a first embodiment, there is provided a method oftesting receiver sensitivity in a radio frequency (RF) devicecomprising: (a) selecting a new test quantity to replace a knownreceiver sensitivity test parameter; (b) determining the relationshipbetween the known receiver sensitivity test parameter and the new testquantity; (c) determining a new test criteria based on the new testquantity in accordance with a defined standard; and (d) conducting areceiver sensitivity test using the now test quantity and the new testcriteria, wherein the new test quantity has a predetermined andmonotonic relationship with the known receiver sensitivity testparameter, and wherein the new test quantity is read from a basebandprocessor associated with the RF device, and wherein said step ofdetermining a new test criteria comprises: (i) obtaining a plurality ofthe known receiver sensitivity test parameter measurements andcorresponding values of the new test quantity at each of a plurality ofreceived signal strengths; (ii) calculating at each of the plurality ofreceived signal strength levels an average value of the plurality ofsaid known receiver sensitivity test parameter measurements; (iii)plotting the averages of N-sample groups of the corresponding values ofthe new test quantity versus the calculated average values of theplurality of the known receiver sensitivity test parameter measurementsand determining targeted confidence level probability points from theplot; (iv) interpolating between the targeted confidence levelprobability points for different ones of the plurality of receivedsignal strength levels; and (v) determining a pass/fail threshold forthe new test quantity which corresponds to a pass/fail criteriaassociated with the defined test standard

Preferably, the new test quantity is taken from the group comprisingsignal to noise ratio, signal to interference ratio, energy per chip tointerference density ratio (Ec/Io), energy per bit to interferencedensity ratio (Eb/Io), energy per symbol to interference density ratio(Es/Io), energy per chip to noise density ratio (Ec/No), energy per bitto noise density ration (Eb/No), energy per symbol to noise densityratio (Es/No), carrier power to noise density ratio (C/No), correlatedenergy, correlated amplitude, symbol error rate and bit error rate.

In accordance with a second embodiment, there is provided a system fortesting receiver sensitivity in a radio frequency (RF) devicecomprising: (a) a wireless communications test set; (b) a device undertest (DUT) communicating with the wireless communications test set,wherein a simulated traffic signal is forwarded from the wirelesscommunications test set to the DUT, and wherein a receiver sensitivitytest is conducted based on a test criteria in a accordance with adefined standard, the test criteria based on a predeterminedrelationship between a known receiver sensitivity test parameter and anew test quantity, and wherein the DUT comprises a baseband processor,and wherein the baseband processor comprises a channel estimator forestimating the new test quantity associated with the simulated trafficsignal, and wherein the estimated new test quantity is amplitude.

Preferably, the baseband processor further includes a function formapping a correlated energy value derived from said estimated amplitudeto a signal to noise ratio (SNR) or Ec/Io.

More preferably, the wireless communications test set is connected via acoaxial cable to an antenna or radiating coupler positioned in ashielded enclosure housing the DUT, and wherein the DUT receives thesimulated traffic signal via a wireless transmission from the antenna orradiating coupler, and wherein path loss associated with the wirelesstransmission, the coaxial cable, or the antenna or radiating coupler, iscorrected by the wireless communications test set.

In accordance with a third embodiment, a modulated carrier wavegenerated by a wireless communication test set and received by a deviceunder test (DUT), wherein the modulated carrier wave embodies a datasignal representing a simulated traffic signal in a wireless network,and wherein a receiver sensitivity test is conducted based on a testcriteria in accordance with a defined standard, and wherein the testcriteria is based on a predetermined relationship between a knownreceiver sensitivity test parameter and a new test quantity, and whereinthe new test quantity is associated with a quality level of saidreceived modulated carrier wave, and wherein the new test quantity isdetermined at a digital processing portion of the DUT, and wherein thenew test quantity has a predetermined and monotonic relationship withthe known receiver sensitivity test parameter, and wherein the new testquantity is read from a digital baseband processor associated with theRF device.

The advantage of the described test method is now readily apparent.Using the improved testing methodology, the test time using thecorrelated energy or SNR technique can be reduced significantly. Testtime using the FER method can span 48 to 80 seconds per device for oneconfidence level while using the correlated energy or SNR method canreduce the test time to a range of 10 to 22 seconds at the sameconfidence level.

Further features and advantages of the invention will be apparent fromthe detailed description which follows together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention will bc obtained by consideringthe detailed description below, with reference to the following drawingsin which:

FIG. 1 depicts a typical mobile communication system;

FIG. 2 depicts a representative receiver block diagram for a wirelessdevice;

FIG. 3A depicts a standard FER hardware test setup for sensitivity anddynamic range tests;

FIG. 3B depicts a table showing the test parameters associated with astandard FER test according to TIA/EIA/-98E, receiver sensitivity anddynamic range test;

FIG. 4 depicts the steps in the characterization process whereby therelationship of correlated energy to FER is established;

FIG. 5 depicts an energy estimator settle time chart;

FIGS. 6A and 6B depict a plot of FER(i) v. FERave and correlated energyv. FERave along with a plot of the 95% confidence line;

FIGS. 7A to 7E depict exemplary plots of correlated energy v. FER forsample sizes N=5, 10, 20, 40 and 80;

FIG. 8 depicts a table listing iteration criteria used in testing awireless device using correlated energy;

FIGS. 9A and 9B depict the steps for testing a wireless device usingcorrelated energy; and

FIG. 10 depicts the steps for an alternate test on a wireless deviceusing correlated energy.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The first step in the testing methodology, is the energy or SNR and FERcharacterization. As those in the art will appreciate, one of the mainadvantages of CDMA systems is the capability of using signals thatarrive in the receivers with different time delays. This phenomenon iscalled multipath. As discussed in the background section, CDMA wirelessdevices may use RAKE receivers located in baseband processor 310. A RAKEreceiver uses several baseband correlators to individually processseveral signal multipath components. Each correlator in a RAKE receiveris called a RAKE-receiver finger. One of the receivers (fingers) usuallyis a dedicated channel searcher which obtains course estimates of thetime and amplitude of arrival of the strongest multipath components ofthe wireless device signal. This information is then feet to the otherfingers. Each finger then demodulates the signal corresponding to astrong multipath. The results are then combined together to make thesignal stronger. The square of the amplitude at the correlator output isgenerally referred to as the correlated energy. Baseband processor 310also includes a function which can map the correlator output energy to asignal to interference ratio, Ec/Io, expressed in dB. For the purposesof the present description, the test methodology will be described usingthe correlated energy, although Ec/Io could also be used and is meant tobe included within the scope of the present application.

Prior to taking correlated energy readings it is necessary to determinethe settling time for the correlated energy readings produced by theestimator i.e. to ensure that an erroneous transient reading is notinadvertently taken. This is accomplished by performing a test call atan arbitrarily chosen strong received signal strength (Ior) e.g.—60_dBm.An automated program is then used to set Ior to have a step decrease toa weak level around the device sensitivity, e.g. −105 dBm and anextended diagnostic monitor (XDM), a software tool well known to thoseskilled in the art, is used to read the correlated energy values. Thefrequency of reading by XDM should be chosen to be fast enough to getgood time response samples e.g. live readings per second and anexemplary resulting time response for a sample device under test areshown in FIG. 5. Each point on the graph is a distinct reading ofenergy. The results reveal that a wait time of about 1.5 seconds issufficient to allow for settling of the energy signal.

FIG. 4 is a flow chart depicting the steps in the characterizationprocess; this preparation step must be performed before the wirelessdevice test can be conducted. The process generates a set of testparameters and criteria to be used in the test. For thecharacterization, two alternate objectives can be used. The first is tomake the test method as reliable as an existing FER-based test in termsof false alarm rate (i.e. a good device mistakenly reported as bad), andmissed detection rate (i.e. a bad device is mistakenly reported asgood). The second is to make the new test compliant with the standard,which only controls the missed detection rate lower than 5% (i.e. 1-95%)and does not really care about the false alarm rate. The followingdescribes the former embodiment and then describes the latter.

At step 400, the wireless communications test set (which simulates basestation 120) is configured to the same receiver sensitivity test settingas detailed in TIA/EIA/-98E (see FIG. 3B) and Ior is set, for example,in 0.5 dB steps in a FER range that covers 0.1% 1%. At step 410, adevice under test (DUT) is then tested by, at each of a number ofreceived signal strength (Ior) levels: (a) measuring the FER using themax number of frames that is used in factory e.g. 1000 frames; (b)repeating the measurement for a large number of times e.g. 20 times; (c)recording each individual FER(i) and also calculating the average FER ofall the measured frames of the repeated measurement (denoted as FERave);and (d) simultaneously measuring and recording a large sample orcorrelated energy values for each Ior setting. At step 420, a scatterdiagram of FER(i) vs. FERave is then plotted. At step 430, the 95%probability point is determined (i.e. an FER(i) value of P at whichProb[FER(i)>P]=95%, and similarly an FER(i) value of Q at whichProb[FER(i)<Q]=95%). In the calculation, if the sample size of FER(i) isnot significantly large, such as 20 measurements, the variance of the 20samples is used and Gaussian distribution is assumed to calculate the Pand Q. The 95% confidence lines are then plotted on the graph by ininterpolating all of the P points, and all of the Q points respectively.A graph for a sample device is given in FIG. 6A. As will be appreciatedby those in the art, if a measurement of 1000 frames gets a raw FER(i)reading of X, most likely the a true FER is between 13 and A, and theworst case with 95% confidence is A. When A is FER of 0.5%, find therange between A and 13. This range will help determine the number ofaverages needed in new tests for achieving a sufficiently low falsealarm rate. B is the point on the line of 95% on the other side i.e.,the Prob[FER(i)<Q]=95%.

At step 440, the measured correlated energy samples are grouped by N=5and the average value of each N-sample group is plotted as scatterdiagram. An exemplary graph for a sample device is given in FIG. 6B. Atstep 450, the 95% probability point of the scatters is located, similarto step 430, i.e., Prob[correlated energy(i)>P]=95% and on the otherside Prob[FER(i)<Q]−95%. The point A′=0.5% is located and the rangebetween A′ and B′ is obtained. If the range B′-A′ is larger than thatB-A obtained in step 430, N is increased and steps 440 and 450 arerepeated. Otherwise N is decreased and steps 440 and 450 are repeated.At step 460, the N value determined at step 450 is verified for a numberof sample devices. The N value determined at step 450 is used to measurethe average correlated energy a number of times on each of a number ofsample devices (good and bad) and each of a few channels on each band ofthe supported bands. The corresponding FER around 0.5% is also measuredwith a large number of frames (e.g. 5000 or more). The overall 95%confidence result is then determined to check for consistency and thepass/fail criteria (X and X′ from FIGS. 6A and 6B), for the 0.5% FERwith 95% confidence. For the purpose of compliance with the TIA/EIA/-98Estandard and without taking into account the false alarm rate, N can beany value and only X′ need be determined for the test.

An alternate embodiment using variable N can also be used. To determineN, after the determined settling time of the test Ior, a continuousseries of individual correlated energy samples are taken. The mean of Nadjacent samples is calculated and plotted. The exemplary results for adevice under test are shown in FIGS. 7A to 7E for N=5, 10, 20, 40, and80. These values of N are chosen to simplify the processing of data inthe test stage. Each point on the graphs depicted in FIGS. 7A to 7E isthe scatter diagram of mean values of N adjacent readings. As Nincreases, the 95% confidence interval becomes narrower. Using a testlimit of FER=0.5%, taken from the plot of N=5 (FIG. 7A), thecorresponding correlated energy threshold value is determined to be1385. Thus, a mean correlated energy above 1385, would indicate anFER<0.5%. It Is obviously most desirable to use the lowest value of N todecrease test time i.e. N=5. However, it may not always be possible todetermine a pass with N=5, as the false alarm rate may be too high. If apass is not determined within N=5 samples, then N can be doubled until amaximum value of N=80 is reached. The maximum value of N is determinedby the maximum test time allowed in manufacturing and the sampling ratefor reading the energy values. If the mean of 80 energy readings issmaller than 1333, a fail is registered.

Having completed the characterization step to determine the correlatedenergy pass/fail thresholds, the actual test of the sample device can beconducted. FIG. 8 depicts a table highlighting the number of correlatedenergy readings taken over a given time and the associated passcriterion for each iteration of the test for a sample device under test.The pass criterion are derived from FIGS. 7A to 7E. FIGS. 9A and 9Bdepict a flow chart highlighting the steps in a generic test. In FIG.9A, at step 500 a test call is setup on the test channel to generatesimulated traffic. At step 510, the test Ior is set. At step 520, thetester waits the correlated energy estimator settling time (e.g. 1.5seconds). At step 530, the first iteration is performed. N samples ofcorrelated energy are taken within, for example, one second (where N ispreferably greater than or equal to 5). The average of the N samples isthen taken. If the calculated average is greater than the pass criterionestablished for the number of N samples (see FIGS. 7A and 8) then, atstep 540 the device under test is passed. If the calculated average isbelow the pass criterion, then proceed to iteration two at step 550, Inthe second iteration, an additional N correlated energy samples aretaken and the average of these samples is calculated. The average fromthe first iteration and the second iteration are added together anddivided by two to form an overall average of 2N samples. If the newaverage is greater than the pass criterion established for the number of2N samples (sec FIGS. 7B and 8) then, at step 560, the device under testis passed. If the calculated average is below the pass criterion, thenproceed to iteration three at step 570 in FIG. 9B. The steps associatedwith second iteration are repeated with 2N additional correlated energysamples and the calculated average is compared to the 4N pass criteria.If the new average is greater than the pass criterion established forthe number of 4N samples (see FIGS. 7C and 8) then, at step 580, thedevice under test is passed. If the calculated average is below the passcriterion, then proceed to iteration four at step 590. 4N additionalcorrelated energy samples are taken and the calculated average iscompared to the 8N pass criteria. If the new average is greater than thepass criterion established for the number of 8N samples (see FIGS. 7Dand 8) then, at step 600, the device under test is passed. If thecalculated average is below the pass criterion, then proceed toiteration five at step 610. 8N additional correlated energy samples aretaken and the calculated average is compared to the 16N pass criteria.If the new average is greater than the pass criterion established forthe number of 16N samples (see FIGS. 7E and 8) then, at step 620, thedevice under test is passed. If the calculated average is below the passcriterion, then, at step 630, the device under test is railed andtesting begins on another device. Depending on the number of iterationsa device has to be tested, some devices may take less time to finishtesting than other devices. Overall, the average test time of manydevices is significantly reduced. The number of iterations may not haveto be five. The test which has been described serves only as an example.

FIG. 10 depicts an alternate test in accordance with the presentapplication. At step 700 a test call is setup on the test channel. Atstep 710, the test Ior is set. At step 720, the tester waits thecorrelated energy estimator settling time (e.g. 1.5 seconds). At step730, the first iteration is performed. N samples of correlated energyare taken within, for example, one second (where N is preferably greaterthan or equal to 5). The average of the N samples is then taken. If thecalculated average is greater than the upper pass criterion establishedfor the number of N samples (see FIG. 7A, upper limit for 0.5% FER and95% confidence) then, at step 740 the device under test is passed. Ifthe calculated average is below the lower fail criterion (see FIG. 7A,lower limit for 0.5% FER and 95% confidence) then the device under testis failed at step 750. If the calculated average is between the upperand lower limit, than proceed to step 760. In the second iteration, 3Nadditional correlated energy samples are taken and the average of thesesamples is calculated. The average from the first iteration is weightedby ¼ and the second iteration is weighted by ¾ and then the two weightedvalues are added together to form an overall average of 4N samples. Ifthe newly calculated average is less than the 4N fail criteria then, atstep 770 the device under test is failed. If the newly calculatedaverage is greater than the 4N pass criteria then, at step 780 thedevice under test is passed. The described 4N pass criteria representsthe 50% confidence midpoint between the upper and lower limits for 95%confidence (see FIG. 7C). Similarly, the test can be performed using adifferent number of iterations. The test described is only by way ofexample. As will be appreciated, if the test only allows two possibleresulting decisions: Pass or Fail, the threshold has to be the mid pointand for some devices the confidence or such decision has to be 50%.Alternately, the pass confidence can be 95% and the fail confidence canbe as low as 5%, in which case the threshold used is the upper 95%point. In yet another embodiment, the resulting decision can be one ofthree: Pass, Fail or Uncertain, in which case to determine a device“Pass”, the average must be higher than the upper 95% point, todetermine a device “Fail” the average must be lower than the lower 95%point, and to determine a device “Uncertain”, the average must bebetween the upper and lower 95% thresholds. In this case, both “Pass”and “Fail” decisions have a confidence of 95%.

As will be appreciated by those in the art, the wireless communicationstest set which simulates base station 1220 may be hard wired directly tothe DUT via coaxial cable to an RF connector or the coaxial cable couldbe hard wired to a transmitting antenna or a radiating coupler locatedwithin a shielded box or an RF anechoic chamber where DUT 330 is alsolocated. DUT 330 may be simply a printed circuit board integral to awireless device with the sensitivity test being conducted by feeding atest signal into an antenna port integral to the printed circuit board.It will also be appreciated that path loss introduced by the coaxialcables and/or antenna/couplers/propagation involved in the test set upis accounted for in the tests when setting the Ior value.

Although various exemplary embodiments of the invention have beendisclosed, it should be apparent to those skilled in the art thatvarious changes and modifications can be made which will achieve some ofthe advantages of the improved testing methodology without departingfrom the true scope of the application. More specifically, any physicalquantity obtained in the baseband processing which has a monotonicrelationship with signal to interference ratio can be used to conductthe receiver sensitivity test e.g. symbol error rate (SER), bit errorrate (BER), carrier power to noise density ratio (C/No), energy persymbol to interference density ratio (Es/Io), energy per bit tointerference density ratio (Eb/Io), energy per chip to noise densityratio (Ec/No), energy per bit to noise density ration (Eb/No), energyper symbol to noise density ratio (Es/No) etc. Also, the measurementreplaced by a physical quantity (e.g. signal to interference ratio orcorrelated energy) in a test may not have to be FER. Other examplesinclude packet error rate (PER) or BER after forward error correction.All such alternate embodiments are meant to be included within the scopeof the invention. Additionally, the air interface is not limited tocdma2000. There are other examples including UMTS, GSM/GPRS, 802.11, etcto which the present invention can be applied. Finally, this test hadbeen described in relation to a mobile device. The test is moreuniversally applicable to any RF communication device where receiversensitivity testing is required (e.g. for base station 120 in FIG. 1)where a relationship between the existing test parameter and correlatedenergy or SNR can be determined to establish new thresholds againstwhich the receiver's sensitivity can be evaluated.

A person understanding this invention may now conceive of alternativestructures and embodiments or variations of the above all of which areintended to fall within the scope of the invention as defined in theclaims that follow.

1. A method of testing receiver sensitivity in a radio frequency (RF)device comprising: (a) selecting a new test quantity to replace a knownreceiver sensitivity test parameter; (b) determining the relationshipbetween said known receiver sensitivity test parameter and said new testquantity; (c) determining a new test criteria based on said new testquantity in accordance with a defined standard; and (d) conducting areceiver sensitivity test using said new test quantity and said new testcriteria. wherein said new test quantity has a predetermined andmonotonic relationship with said known receiver sensitivity testparameter, and wherein said new test quantity is read from a basebandprocessor associated with said RF device, and wherein said step ofdetermining a new test criteria comprises: (i) obtaining a plurality ofsaid known receiver sensitivity test parameter measurements andcorresponding values of said new test quantity at each of a plurality ofreceived signal strengths; (ii) calculating at each of said plurality ofreceived signal strength levels an average value of said plurality ofsaid known receiver sensitivity test parameter measurements; (iii)plotting the averages of N-sample groups of said corresponding values ofsaid new test quantity versus said calculated average values of saidplurality of said known receiver sensitivity test parameter measurementsand determining targeted confidence level probability points from saidplot, (iv) interpolating between said targeted confidence levelprobability points for different ones of said plurality of receivedsignal strength levels; and (v) determining a pass/fail threshold forsaid new test quantity which corresponds to a pass/fail criteriaassociated with said defined test standard.
 2. The method of claim 1wherein said new test quantity is taken from the group comprising signalto noise ratio, signal to interference ratio, energy per chip tointerference density ratio (Ec/Io), energy per bit to interferencedensity ratio (Eh/Io), energy per symbol to interference density ratio(Es/Io), energy per chip to noise density ratio (Ec/No), energy per bitto noise density ration (Eb/No), energy per symbol to noise densityratio (Es/No), carrier power to noise density ratio (C/No), correlatedenergy, correlated amplitude, symbol error rate and bit error rate. 3.The method of claim 1 wherein said known receiver sensitivity testparameter is taken from the group comprising frame error rate (FER) andpacket error rate (PER).
 4. The method of claim 1 wherein said step ofconducting comprises: (a) waiting a defined settling time; (b) obtainingN samples of said new test quantity; (c) calculating the average of theN samples, (d) if said calculated average is greater than a specified Nnew test quantity threshold, passing said wireless device, (e) else, ifsaid calculated average is less than said specified N new test quantitythreshold, obtaining a multiple number or N additional samples andrepeating steps (c) and (d); and (e) after a predefined number ofiterations, failing said RF device if said new test quantity thresholdhas not been met.
 5. The method of claim 1 wherein said stepo'conducting comprises: (a) waiting a defined settling time; (b)obtaining N samples of said new test quantity; (c) calculating theaverage of the N samples; (d) if said calculated average is greater thanan upper limit associated with a specified N test quantity threshold,passing said wireless device, (e) else, if said calculated average isless than said upper limit associated with said N new test quantitythreshold but greater than a lower limit associated with said N testquantity threshold, obtaining 3N additional samples and repeating steps(c) and (d) wherein a calculated 4N average is obtained by assigningsaid N samples a weighted average of ¼ and said 3N samples a weightedaverage of ¼; and (f) if said 4N calculated average is less than aspecified 4N new test quantity threshold, failing said RF device.
 6. Themethod of claim 1 wherein said defined standard is TIA/EIA/-98E, andwherein said correlated energy thresholds correspond to a forward errorrate (FER) less than or equal to 0.50% with 95% confidence.
 7. Themethod of claim 6 wherein said known receiver sensitivity test parameteris frame error rate and said new test quantity is correlated energy, andwherein said step of determining a new test criteria comprises: (a)obtaining a plurality or FER measurements and corresponding correlatedenergy values at each of a plurality of received signal strengths; (b)calculating an average value of said plurality of FER measurementsobtained at each of said plurality of received signal strengths; (e)plotting said plurality of FER measurements versus said calculated FERaverages and determining the 95% probability point from said plot; (d)plotting the averages of N-sample groups of said correspondingcorrelated energy values versus said calculated FER averages anddetermining the 95% probability points from said plot; (e) interpolatingbetween the 95% probability points for different ones of said pluralityof received signal strength levels; and (f) determining a correlatedenergy threshold for 0.5% FER with 95% confidence.
 8. The method ofclaim 7 wherein said step of conducting comprises: (a) waiting a definedsettling time; (b) obtaining N samples of said correlated energy; (c)calculating the average of the N samples; (d) if said calculated averageis greater than a specified N correlated energy threshold, passing saidwireless device; and (e) else, if said calculated average is less thansaid specified N correlated energy threshold, obtaining a multiplenumber of N additional samples and repeating steps (c) and (d); and (f)after a predefined number of iterations, failing said RF device if saidcorrelated energy threshold has not been met.
 9. The method of claim 7wherein said step of conducting comprises: (a) waiting a definedsettling time; (b) obtaining N samples of said correlated energy; (c)calculating the average of the N samples; (d) if said calculated averageis greater than an upper limit associated with a specified N correlatedenergy threshold passing said wireless device; and (e) else if saidcalculated average is less than said upper limit associated with saidspecified N correlated energy threshold but greater than a lower limitassociated with said specified N correlated energy threshold, obtaining3N additional samples and repeating steps (c) and (d) wherein acalculated 4N average is obtained by assigning said N samples a weightedaverage of ¼ and said 3N samples a weighted average of ¾; and (f) ifsaid 4N calculated average is less than a specified 4N correlated energythreshold, failing said RF device.
 10. The method of claim 7 whereinstep (a) further comprises the step of translating said correlatedenergy values to corresponding signal to noise ratio (SNR) or Ec/Iovalues, and wherein steps (d), (c) and (f) are performed using saidmapped SNR or Ec/Io values.
 11. The method of claim 8 wherein step (b)further comprises the step of translating said correlated energy valuesto corresponding signal to noise ratio (SNR) or Ec/Io values, andwherein steps (c) to (f) are performed using said mapped SNR or Ec/Tovalues.
 12. The method of claim 1 wherein said new test criteriadetermined in step (c) achieves a defined missed detection rate and adefined false alarm rate.
 13. A system for testing receiver sensitivityin a radio frequency (RF) device comprising: (a) a wirelesscommunications test set; (b) a device under test (DUT) communicatingwith said wireless communications test set, wherein a simulated trafficsignal is forwarded from said wireless communications test set to saidDUT, and wherein a receiver sensitivity test is conducted based on atest criteria in a accordance with a defined standard, said testcriteria based on a predetermined relationship between a known receiversensitivity test parameter and a new test quantity, and wherein said DUTcomprises a baseband processor, and wherein said baseband processorcomprises a channel estimator for estimating said new test quantityassociated with said simulated traffic signal, and wherein saidestimated new test quantity is amplitude.
 14. The system of claim 13wherein said RD device is a wireless device operating within a wirelessnetwork.
 15. The system of claim 13 wherein said RF device is a basestation operating within a wireless network.
 16. The system of claim 13wherein said RF receiver is arranged on a printed circuit board integralto said wireless device, and wherein said receiver sensitivity test isconducted by feeding said simulated traffic signal into an antenna portintegral to said printed circuit board.
 17. The system of claim 13wherein said baseband processor further includes a function fortranslating a correlated energy value derived from said estimatedamplitude, to a signal to noise ratio (SNR) or Ec/Io.
 18. The system ofclaim 13 wherein said wireless communications test set is connected viaa coaxial cable to an antenna or radiating coupler positioned in ashielded enclosure housing said DUT, and wherein said DUT receives saidsimulated traffic signal via a wireless transmission from said antennaor radiating coupler, and wherein path loss associated with saidwireless transmission, said coaxial cable, or said antenna or radiatingcoupler, is corrected by said wireless communications test set.
 19. Amodulated carrier wave generated by a wireless communication test setand received by a device under test (DUT), wherein said modulatedcarrier wave embodies a data signal representing a simulated trafficsignal in a wireless network, and wherein a receiver sensitivity test isconducted based on a test criteria in accordance with a definedstandard, and wherein said test criteria based on a predeterminedrelationship between a known receiver sensitivity test parameter and anew test quantity, and wherein said new test quantity is associated witha quality level of said received modulated carrier wave, and whereinsaid new test quantity is determined at a digital processing portion ofsaid DUT, and wherein said new test quantity has a predetermined andmonotonic relationship with said known receiver sensitivity testparameter, and wherein said new test quantity is read from a digitalbaseband processor associated with said RF device.
 20. The modulatedcarrier wave of claim 19 wherein said new test quantity is taken fromthe group comprising signal to noise ratio, signal to interferenceratio, energy per chip to interference density ratio (Ec/Io), energy perbit to interference density ratio (Eb/Io), energy per symbol tointerference density ratio (Es/Io), energy per chip to noise densityratio (Ec/No), energy per bit to noise density ration (Eb/No), energyper symbol to noise density ratio (Es/No), carrier power to noisedensity ratio (C/No), correlated energy, correlated amplitude, symbolerror rate and bit error rate.
 21. The modulated carrier wave of claim19 wherein said known receiver sensitivity test parameter is taken fromthe group comprising frame error rate (FER) and packet error rate (PER).